diff options
author | Paolo Bonzini <pbonzini@redhat.com> | 2017-08-21 18:58:56 +0200 |
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committer | Paolo Bonzini <pbonzini@redhat.com> | 2017-09-22 01:06:51 +0200 |
commit | 7c9e527659c67d4d7b41d9504f93d2d7ee482488 (patch) | |
tree | 2f604a8ad523e8cf9217b464344900f86d0bbfba /include | |
parent | 092aa2fc65b7a35121616aad8f39d47b8f921618 (diff) |
scsi, file-posix: add support for persistent reservation management
It is a common requirement for virtual machine to send persistent
reservations, but this currently requires either running QEMU with
CAP_SYS_RAWIO, or using out-of-tree patches that let an unprivileged
QEMU bypass Linux's filter on SG_IO commands.
As an alternative mechanism, the next patches will introduce a
privileged helper to run persistent reservation commands without
expanding QEMU's attack surface unnecessarily.
The helper is invoked through a "pr-manager" QOM object, to which
file-posix.c passes SG_IO requests for PERSISTENT RESERVE OUT and
PERSISTENT RESERVE IN commands. For example:
$ qemu-system-x86_64
-device virtio-scsi \
-object pr-manager-helper,id=helper0,path=/var/run/qemu-pr-helper.sock
-drive if=none,id=hd,driver=raw,file.filename=/dev/sdb,file.pr-manager=helper0
-device scsi-block,drive=hd
or:
$ qemu-system-x86_64
-device virtio-scsi \
-object pr-manager-helper,id=helper0,path=/var/run/qemu-pr-helper.sock
-blockdev node-name=hd,driver=raw,file.driver=host_device,file.filename=/dev/sdb,file.pr-manager=helper0
-device scsi-block,drive=hd
Multiple pr-manager implementations are conceivable and possible, though
only one is implemented right now. For example, a pr-manager could:
- talk directly to the multipath daemon from a privileged QEMU
(i.e. QEMU links to libmpathpersist); this makes reservation work
properly with multipath, but still requires CAP_SYS_RAWIO
- use the Linux IOC_PR_* ioctls (they require CAP_SYS_ADMIN though)
- more interestingly, implement reservations directly in QEMU
through file system locks or a shared database (e.g. sqlite)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'include')
-rw-r--r-- | include/scsi/pr-manager.h | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/include/scsi/pr-manager.h b/include/scsi/pr-manager.h new file mode 100644 index 0000000000..b2b37d63bc --- /dev/null +++ b/include/scsi/pr-manager.h @@ -0,0 +1,56 @@ +#ifndef PR_MANAGER_H +#define PR_MANAGER_H + +#include "qom/object.h" +#include "qapi/qmp/qdict.h" +#include "qapi/visitor.h" +#include "qom/object_interfaces.h" +#include "block/aio.h" + +#define TYPE_PR_MANAGER "pr-manager" + +#define PR_MANAGER_CLASS(klass) \ + OBJECT_CLASS_CHECK(PRManagerClass, (klass), TYPE_PR_MANAGER) +#define PR_MANAGER_GET_CLASS(obj) \ + OBJECT_GET_CLASS(PRManagerClass, (obj), TYPE_PR_MANAGER) +#define PR_MANAGER(obj) \ + OBJECT_CHECK(PRManager, (obj), TYPE_PR_MANAGER) + +struct sg_io_hdr; + +typedef struct PRManager { + /* <private> */ + Object parent; +} PRManager; + +/** + * PRManagerClass: + * @parent_class: the base class + * @run: callback invoked in thread pool context + */ +typedef struct PRManagerClass { + /* <private> */ + ObjectClass parent_class; + + /* <public> */ + int (*run)(PRManager *pr_mgr, int fd, struct sg_io_hdr *hdr); +} PRManagerClass; + +BlockAIOCB *pr_manager_execute(PRManager *pr_mgr, + AioContext *ctx, int fd, + struct sg_io_hdr *hdr, + BlockCompletionFunc *complete, + void *opaque); + +#ifdef CONFIG_LINUX +PRManager *pr_manager_lookup(const char *id, Error **errp); +#else +static inline PRManager *pr_manager_lookup(const char *id, Error **errp) +{ + /* The classes do not exist at all! */ + error_setg(errp, "No persistent reservation manager with id '%s'", id); + return NULL; +} +#endif + +#endif |